It took me a while, but here is how I solved it myself. It's probably a variation of caveman_dick's third option.
1) Add new action into UISequence to back up your current config file. You can do it with the magic of custom action and ComponentSearch to actually locate the file.
2) Restore the file later in ExecuteSequence.
<Binary Id="CustomActions.CA.dll" SourceFile="..\CustomActions\bin\$(var.Configuration)\CustomActions.CA.dll" />
<CustomAction Id="BackupConfigFile"
Return="check"
BinaryKey="CustomActions.CA.dll"
DllEntry="BackupFile" />
<CustomAction Id="RestoreConfigFile"
Return="check"
Execute="deferred"
Impersonate="no"
BinaryKey="CustomActions.CA.dll"
DllEntry="RestoreFile" />
<CustomAction Id="PropertyDelegator"
Property="RestoreConfigFile"
Value="MYTARGET=[MYTARGET];FILENAME_TO_BACKUP=[FILENAME_TO_BACKUP]" />
<Property Id="FILENAME_TO_BACKUP" Value="test.exe.config" />
<Property Id="PREVIOUS_PATH">
<ComponentSearch Id="evSearch" Guid="{010447A6-3330-41BB-8A7A-70D08ADB35E4}" />
</Property>
and here is quick CustomAction.cs I wrote:
[CustomAction]
public static ActionResult BackupFile(Session session)
{
try
{
// check out if the previous installation has our file included
// and if it does,
// then make copy of it.
var previousInstallationPath = session["PREVIOUS_PATH"];
var fileToBackup = session["FILENAME_TO_BACKUP"];
if (!string.IsNullOrEmpty(previousInstallationPath) && !string.IsNullOrEmpty(fileToBackup))
{
var absolutePath = Path.Combine(previousInstallationPath, fileToBackup);
if (File.Exists(absolutePath))
{
var destinationPath = Path.Combine(Path.GetTempPath(),
string.Concat(fileToBackup, _MODIFIER));
File.Copy(absolutePath, destinationPath);
}
}
}
catch (Exception e)
{
session.Log("Couldn't backup previous file: {0}", e);
}
return ActionResult.Success;
}
[CustomAction]
public static ActionResult RestoreFile(Session session)
{
try
{
// check if our CustomAction made backup of file,
// and if it indeed exists in temp path, then
// we basically copy it back.
var currentInstallationPath = session.CustomActionData["MYTARGET"];
var fileToRestore = session.CustomActionData["FILENAME_TO_BACKUP"];
var fileOriginalContentPath = Path.Combine(Path.GetTempPath(),
string.Concat(fileToRestore, _MODIFIER));
if (File.Exists(fileOriginalContentPath))
{
var destinationFile = Path.Combine(currentInstallationPath, fileToRestore);
if (File.Exists(destinationFile))
File.Delete(destinationFile);
File.Move(fileOriginalContentPath, destinationFile);
}
}
catch (Exception e)
{
session.Log("Couldn't restore previous file: {0}", e);
}
return ActionResult.Success;
}
to actually define sequences:
<InstallUISequence>
<Custom Action="BackupConfigFile" After="AppSearch"></Custom>
</InstallUISequence>
<InstallExecuteSequence>
<Custom Action="PropertyDelegator" Before="RestoreConfigFile" />
<Custom Action="RestoreConfigFile" After="InstallFiles"></Custom>
</InstallExecuteSequence>
haven't tested it thoroughly, but seems to do the job for now. Caveat: Temp folder might change?!
Alternatively there is this one that I found from Internet, but haven't tested it.
<!-- Support Upgrading the Product -->
<Upgrade Id="{B0FB80ED-249E-4946-87A2-08A5BCA36E7E}">
<UpgradeVersion Minimum="$(var.Version)"
OnlyDetect="yes" Property="NEWERVERSIONDETECTED" />
<UpgradeVersion Minimum="0.0.0"
Maximum="$(var.Version)" IncludeMinimum="yes"
IncludeMaximum="no"
Property="OLDERVERSIONBEINGUPGRADED" />
</Upgrade>
<Property Id="OLDERVERSIONBEINGUPGRADED" Secure="yes" />
<!-- Action to save and Restore the Config-File on reinstall
-->
<!-- We're using CAQuietExec to prevent DOS-Boxes from
popping up -->
<CustomAction Id="SetQtCmdLineCopy" Property="QtExecCmdLine"
Value=""[SystemFolder]cmd.exe" /c copy
"[INSTALLDIR]MyApp.exe.config"
"[INSTALLDIR]config.bak"" />
<CustomAction Id="QtCmdCopy" BinaryKey="WixCA"
DllEntry="CAQuietExec" Execute="immediate" />
<CustomAction Id="SetQtCmdLineRestore"
Property="QtCmdRestore" Value=""[SystemFolder]cmd.exe" /c move
/Y "[INSTALLDIR]config.bak"
"[INSTALLDIR]MyApp.exe.config"" />
<CustomAction Id="QtCmdRestore" Execute="commit"
BinaryKey="WixCA" DllEntry="CAQuietExec" />
<!-- These actions will run only for a major upgrade -->
<InstallExecuteSequence>
<Custom Action="SetQtCmdLineCopy"
After="InstallInitialize"> NOT (OLDERVERSIONBEINGUPGRADED = "")</Custom>
<Custom Action="QtCmdCopy"
After="SetQtCmdLineCopy">NOT (OLDERVERSIONBEINGUPGRADED = "")</Custom>
<Custom Action="SetQtCmdLineRestore"
Before="InstallFinalize">NOT (OLDERVERSIONBEINGUPGRADED = "")</Custom>
<Custom Action="QtCmdRestore"
After="SetQtCmdLineRestore">NOT (OLDERVERSIONBEINGUPGRADED =
"")</Custom>
</InstallExecuteSequence>
